Various systems for automatic braking of vehicles are known, where the systems are used in order to avoid or mitigate collisions between a vehicle and other objects, such as other vehicles or obstacles in a road environment.
Many systems are based on a single target approach, i.e., on how much a driver has to brake or steer in order to avoid an object. This is related to the available acceleration in terms of road friction, and may be used to determine when a collision is unavoidable. Ideally, the system only intervenes when the driver needs help.
In systems based on a single target approach, where the threat level for the single most threatening object is evaluated, important aspects may be missed. For example, the combined threat of several objects can be significantly higher than the individual threat of all objects if they are considered separately. For a general traffic situation with multiple objects present, a multi-target threat assessment may be advantageous, but it is difficult to find the required acceleration to avoid a collision.
EP2169500A1 discloses a method of assessing vehicle paths in a road environment including a host vehicle and external objects. The method is including the steps of detecting external objects by a sensor system and generating a plurality of paths passing said external objects. The method of EP2169500A1 describes a search tree method, and uses piecewise constant lateral acceleration for the description of the lateral motion of a vehicle travelling the paths. Although this approximation may be sufficient when used for threat assessment in auto brake systems, it may be insufficient as a base for lateral control of the vehicle since the lateral acceleration cannot change instantly.